61-64
OXYGEN, DISSOLVED, LR, continued
c) Determine the dissolved oxygen concentration according to the
preceding procedure. The result should be 0 ±1 µg/L.
INTERFERENCES
Excess amounts of sodium thioglycolate, sodium ascorbate, sodium
ascorbate + sodium sulfite, sodium ascorbate + cupric sulfate, sodium
nitrite, sodium sulfite, sodium thiosulfate, and hydroquinone will not
reduce the oxidized form of the indicator solution; therefore, they do not
cause significant interference. A 100,000-fold excess of hydrazine will
begin to reduce the oxidized form of the indicator solution.
Sodium hydrosulfite will reduce the oxidized form of the indicator
solution and will cause a serious interference.
STATISTICAL EVALUATION
A single operator repetitively tested samples of the same solutions, using
one DR/700 and two representative lots of AccuVacs. Testing
300 µg/L O
2
samples, the standard deviation was ±27.7 µg/L O
2
.
Testing zero concentration samples, the limit of detection was
16.1 µg/L O
2
. The limit of detection was calculated as three times the
standard deviation when testing zero concentration samples (Adapted
from Analytical Chemistry, 1980, 52, 2242-2249).
SUMMARY OF METHOD
The Low Range Dissolved Oxygen AccuVac Ampul contains reagent
vacuum sealed in a 12-mL ampul. When the AccuVac ampul is broken
open in a sample containing dissolved oxygen, the yellow solution will
turn blue. The blue color development is proportional to the
concentration of dissolved oxygen.
REQUIRED REAGENTS
Quantity
Description Per Test Unit Cat. No.
Low Range Dissolved Oxygen
AccuVac Ampuls . . . . . . . . 1 ampul . . . . 25/pkg . . . . . . . . 25010-25
REQUIRED APPARATUS
Beaker, 50 mL . . . . . . . . . . . . . 1 . . . . . . . . .each . . . . . . . . . . . . 500-41
DR/700 Filter Module
Number 60.01. . . . . . . . . . . 1 . . . . . . . . . each . . . . . . . . . . 46261-00
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